Secret radiant telephony



Am @o 9 J. M. HAMM m SECRET RADIANT TELEPHGM 2 :emma-Smm 1 Filed Dec. 2,w22@ aamsvm E. amQmN condom mv on m 2mg E. 0.25m @5.5% E DE@ M, wz@

J. H. MAA/2Mo, m SECRET RADIANT TELEPHONY- Filed Dec; 2', 1922 2Sheets-Shaw 2 Patented Augo l?, 19260 JOHN HAMMOND, JR., OF GLOUCESTER,MASSACHUSETTS.

f EEGRET RADIANT TELEPHONY.

Application led December This invention relates to the transmission cfintelligence by radiant energy and more particularly tol systems ofsecret radiant telephony. f

An object of theinvention is to provide a system comprising a sendingstation arranged to emit radiant energy of varying character and areceiving station co-operating therewith and provided with apparatusresponsive to the emitted energy despite the variations therein. Morespecifically, a further object of the invention is to provide improvedmeans for the emission of radiant energy in the form of oscillationshaving a fundamental frequency, modulated at successively varyingsupersonic frequencies each made eective and modulated by desiredsignals, such for example as voice Waves, and to arrange for theselective reception of such energy and its transformation into sensiblemanifestations.

p Further objects of the invention will appear from the followingdescription taken in connection withfthe accompanying drawings forming apartof this application and in which- Figure 1 is a diagram of a sendingstation which` is an embodiment of the present invention;

'Figure 2 is a table showing the combination of frequencycharacteristics of the emitted wave; and

Figure 3 is a diagram of one form `of receiving station arranged toco-operate with the sending station of Figure 1.

The system of the present invention employs at its sending station 'acarrier wave of relatively high frequency upon which there is impressedat. different times, differently characterized series .of amplitudevariations of supersonic frequencies relatively lower than that of thecarrier wave, each of the series'of amplitude variations being madeeffective by speech or other desired signals and being modulatedthereby. Changes in the characterization of the periodic amplitudevariations may be made erratically or in accordance with the will of anoperator, and thev carrier rfrequency may also be changed from one toanother of a plurality of different, predetermined values.

ln a general way the receiving set may be desribed'as comprising aplurality of resonant channels, each including a circuit tuned to one ofthe carrier frequencies mentioned 2,1922. serial ne. ceases.

above and connected to other circuits which are tuned to the lower,supersonic frequencies, with detecting or rectifying means for each ofthe channels and a single indicating device. ln combination with suchreceiving elements apparatus may be used which provides energy at thelower, supersonic frequencies of the sending station.

Referring more in detail to Fig. 1, there is shown a source of highfrequency, said source being in this case a thermionic device 10, havinga usual heated filament 1l for emitting electrons, a plate 12 upon whichthe electrons impinge, and a grid 13 for controlling the passage ofelectrons. l"Friese parts are connected with inter-related,inductively-coupled circuits in 'such a manner that the energy in theplate circuit reacts on th grid circuit so as to cause the device tooscillate. There is thus produced an oscillatory current of a relativelyhigh frequency determined by the electrical constants of theinter-related circuits.

For producing oscillations of relatively lower but supersonic frequencythere is provided a thermionic device 2O having a usual, heated filament11, plate 12 and grid 13. rThis device is connected in a regenerative 1-circuit comprising a transformer having windings 22, 23 and 24e, whichare connected in the plate, grid and secondary output circuitsrespectively. The plate 12 of the device 2O is maintained at a positivepotential with respect tothe filament by means of a usual VI battery 25,the positive terminal of which is connected through an inductance 26 tothe plate. The regenerative circuit is provided with a stoppagecondenser 29 and a suitable Variable condenser 30, the capacity ofwhicl.l maybe adjusted so that oscillations of a predetermined frequencyrelatively lower than that of the master oscillator are gcnerated. Forexample, a current havingl a frequency of 7 0,000 cycles may thus beproduced.

For transforming or stepping up voice or other signalling currents intocurrents having asupersonic frequency range less than the frequency ofthe master oscillator l() and retaining the characteristic variationsofthe signalling currents, the output circuit of the generator isconnected withl a signal modulator comprising a transformer 40 havingits primary winding connected in series with a signal transmitter, inthis case a telephone transmitter 42, and its seccircuits of thethermionic ondary windings respectively connected in the input circuitsof apair of thermlonic devices 43 and 44, each having a customary,heated filament, plate and rid. The output devices 43 and 44 include theprimary windings of a coupling transformer 45 and a common,plate-potential battery 46. The secondary wmdmg of the transformer 45 isconnected to armatures 46 and 47 of a rela, 48. The winding 24 and thewindings o the transformer` V45 are so arranged that the electro-motiveforces induced in the secondary winding of the transformer 45 duringoperation 'of the generator 20 are normall `equal and op posite, andthus currents o the lower, supersonic frequency produce substantiallynoeffect therein, except when the transmitter 42 is producing currentvariations. .Thus a so-called push-pull modulator is obtained, vby meansof which electromotive forces corresponding to the two 51de bands of thevoice-modulated, lower,.supersonic lfrequency generated by the device 20may be produced in the secondary winding of the transformer 45.

For selecting a desired filter, the back contacts 'of the armatures 46and 47 n'are connected to 'armatures 50 and 51 of a second relay 52, thenormally closed contacts of which are connected to a band filter 53,while the normally open contacts of the armatures 50 and 51 of the relay52 are connected to a differently characterized band filter 54 and thenormally open contacts of the armatures 46 and 47 of the relay 48 areconnected to a still differently characterized band filter 55. Byoperating one of these relays, or leaving them deenergized, a desiredone of the filters 53, 54 and 55 may be used. The band filter 53comprises a' suitable combination of inductances and condensers such asto rents of adesired requency band, for example, 68,000 to 69,800 cyclesper second; the band filter 54 is constructed to transmit currents of,for example, 43,000 to 44,800 cycles; and the band lter 55, currents of,for example, 23,000 to 24,800 cycles. The

band filters are designed to suppress currents of other than therespective bands of,

frequencies. An auxiliary contact 56 on 'the relay 48 is) provided forshunting an auxiliary condenser 57 around the fr uency ad' justingcondenser 30. The capacity of the condenser 57 is adjusted so that whenthe relay 48 is operated to connect the filter 55 into circuit a changeis simultaneously made in the frequency of the current produced by theoscillator 20 so that this current when modulated by the signal currentproduces a frequency band for A whichl the respective band filter 55 isdesigned. Similarly when the relay 52 isnactuated there is connectedermit the flow of cur-v madam into circuit by its auxiliary contact 58,a shunting condenser 59, the capacity of which is such that the currentsproduced by the oscillator and modulated by voice currents produce afrequency band for which the band filter 54 is designed. In the presentinstance, the condenser 57 in shunt with the condenser 30 causes theoscillator 20 to produce currents o'f 25,000 cycles; and condensers59and- 30 in parallel cause the oscillator 20 to produce currents of45,000 cycles. j

The outputs of the .filter circuits are connected to the input circuitof a modulator comprising ar thermionic device 61 having a usualfilament, plate and grid. The late circuit of the device 61 includes anin uctance 62 and a battery, both of which toether with a winding 63 arealso connected 1n the plate circuitv of the master oscillator 12. Thewinding 63 forms part of a couling transformer 64, the secondary winding65 of which is connectedin the circuit of an antenna 66. Accordingly,the amount of energy supplied to the antenna by the master oscillator 10is varied upon operation of the device 61.

For varying the frequency of oscillation of the device l0 there isprovided a pair of relays and 71, the contacts of which connect intocircuit condens'ers 72 and 73 respectively, the capacities of whichare'selected so as to change the characteristics of the circuit of theoscillator 10 to change the fundamentalfrequency produced thercby todesired amounts. For example, if the fundamental frequenc generated bythe oscillator 10 with con ensers 72 and 73 out of circuit is 1,000,000cycles per second, the capacity ofthe condenser 72 may be such as tocause it to provide currents of,

.switch points as designated in Figure 1.

The normal position of the arm as shown is numbered l. In this positionnone of the relays is operated, and thus the energy emitted has the formof oscillations of, for example, 1,000,000 cycles per second havingperiodic variations impressed thereon of from 68,000 to 69,800 cyclesper second, it being assumed that the frequency of the voice currentsimpressed upon the transmitter 42 varies between 200 and 2000 cycles andthat the filter 53 suppresses the upper side band. The table showssuccessively the fundamental frequency and the varia- .velope of theoutput current of the detector. of the switch (last two columns) and intion frequency for the successive positions the 2nd and 3rd columnsdesignates the actuated relays. ln position 2, for example, a circuit isclosed from grounded battery, winding of relay 70, contact 2, and 'arm80, contact 2, winding of relay 52 to ground, operating relays and 52and connecting into circuit condensers 72 and v59 and 'the hand iilter54. ln position 3, for example, a circuit is closed from groundedbattery,

" resistance coil 8l, contact 3, and arm 80, .l5

contact 3, winding of relay 48-to ground, operating relay 18 andconnecting into'circuit condenser 57 and the band filter 55.

ln the form of receiving stationillustrated inFigure 3, there isprovided a receiving element of such nature as to intercept Hertzianwaves and be capable of having oscillations set up therein in responseto such Waves.. As shown, an antenna 100 of well known type is used,coupled to a closed, oscillatory circuit 101 comprising an inductance102 and a condenser 103. The capacity of the condenser is selected sothat the closed, oscillatory circuit 101 is tuned to one of thefundamental frequencies used, for example, the circuit may be tuned to1,000,000 cycles per second. A second condenser 104C may be connected inarallel with the condenser 103, when desired, so

as to render the closed oscillatory circuit responsive to currents ofanother ofthe fundamental frequencies used, for example, 900,000 cyclesper second. Similarly, a third condenser 105 may be connected inparallel with the condenser 103, when desired, so as to render theclosed, oscillatory circuit responsive to. currents of still another ofthe fundamental frequencies used, forv example, 800,000 cycles persecond. The condensers 104 and 105 are .connected into circuit byswitching devices, such as relays 106 and 107 respectively.l y

vFor detecting the received energy topro duce the lower, supersonic.currents, there'is provided a detector 110, Vwhich may be athree-electrode, thermionic vacuum tube having a usual filament, plateand grid. A; filament-heatin battery 111 supplies current to incan escethe filament, and arranged in shunt with this batteryV is apotentiometer 1.12 having a slider 113 connected to the associated,closed, oscillatory circuit whereby the normal potential of the grid ofthe tliermionie device 110 may be adjusted. A plate-potential'battery114 of suitable volta e maintains a positive potential on the p ate ofthe therniionic. device with respect to its filament, there beingincluded in this circuit four inductanccsin series. These inductancesform primary windings of coupling transformers 115, 116,

117, 118, respectively, through which is induced a'current correspon ingto the en- A. by-pass condenser 119 is provided in shunt with theprimary windings of the transformers 115, 116 and 117 collectively,

so that the high frequency variations in the output of the device 1Qfind a path through the condenser 119 and the primary winding of thetransformer 118. High frequencyY currents are thus induced in thesecondary winding of the transformer 118.

For detecting the high frequency currents induced in the secondarywinding of the transformer 118 and operating a relay thereby, there isprovided a thermionic device 120 having a customary heated filament,

plate and grid. 'llhe in ut of this device is connected to`the secon arywinding of the' transformer 118, a potentiometer 121 and its associatedslider 122 being connected in the circuit in orde'r to control thenormal grid potential. The late of the device 120 is maintained norma yat a positive potential with respect to the filament thereof by means ofa suitable source of plate tial, such as a battery 123. Included inthelate circuit is the. Winding of a relay 1.24: having a ley-passcondenser 125 .1n shunt therewith. The relay 124: is provided with anormally open contact arranged to be otenclosed upon energization of therelay winding and to control they circuit of a ma et 126 and operatingbattery 127. Agia or so-called C battery 128 may also e employed inmaintaining a desired normal potential on the grid of the device'120.

Cooperating with the mafrnet 126 1s an armature 130 havinga aw 131pivotally secured to the free end o the armature and engaging the teethof a ratchet wheel 132.

The teeth are arranged so that energization of the magnet 126 andconsequent attraction fof the armature 130 pulls the pawl 131 forward toengage the next tooth. The armature 130 is provided with a retractilespring, not shown, whereby upon deenergization of the magnet- 126 theratchet wheel 132 1s moved one step in a clockwise direction. The wheel132 vis mounted on a suitable switch shaft 132 upon which is alsomounted a switch arm 133 insulated therefrom. Each. time the magnet 126is operated and released they arm 133 is moved .one step in a clockwisedirection. 'ln the path of movement of the ends of the arm 133 is anarcuate row of contacts positioned to contact with the arm in successivestopping positions of the arm. The arm is shown in the normal position,and in each of the other positions iferent combinations of circuits areclosed for apurpose which will subse uently be s et forth.

The input, circuit of t ie device 120 is noriimllyl tuned by means of acondenser 140 .to a frequency corresponding 4to the .fundamentalfrequency of the energy emitted by the sending station of Figure 1 whenrela s 70 and 71 are deenergized, for examp e, 1,000,000 cycles persecond. A second condenser 141 may be connected in parallel with thecondenser 140 when desired, as by the operation of the relay 106 theright hand armature and front contact of which closes the circuit of thecondenser 141. Thus by the operation of the relay 106 the input cir-Vcuit ofthe device 120 is tuned to a different frequency, which may bethe fundamental frequency of the energy emitted by the sending stationof Figure 1, when relay 70 is operated, for example, 900,000 cycles persecond. Similarly, a third condenser 142, the circuit of which iscontrolled by the right hand armature and front contact of the relay107, may thereby be connected in parallel with the condenser 140 so asto ren der the input circuit of the device 120 resonant to currents ofstill another frequency, corresponding to the fundamental frequency ofthe energy emitted by the sending station of Figure 1 when relay 7l isoperated, for example, 800,000 cycles per second.

For conducting currents corresponding to the supersonic, periodic,amplitude variations impressed upon the energy emitted liti from thesending station of Figure 1, there is provided a filter circuit for eachof the bands of frequencies so impressed. For example, there isconnected to the secondary windings of the transformers 115, 116 and 117a corresponding plurality of filters such as 222, 221 and 220. Thesefilters are designed to pass currents of desired bands of frequencies.For example, the filter 220 is designed to pass currents of 68,000 to69,800 cycles inclusive; the filter 221 currents of 43,000 to 44,800cycles inclusive, and the filter 222 currents of 23,000 to 24,800 cyclesinclusive. The outputs of the filters are connected to the input of adetector 223 through coupling transformers 224, 225 and 226, theconnection being controlled by electro-magnetic switching devices suchas 227, 228 and 229 respectively. The detector 223 may take f the formof a usual three-electrode, thermionic, vacuum tube, having a customaryheated filament, plate and grid and having a potentiometer associatedtherewith for malntaining its grid at a desired normal potential withrespect to its filament.

For producing energy corresponding in frequency to that of theoscillatory current suppressed at the sending station, there 'isincluded in the output of each filter 224, 225, 226 the secondarywinding of a transformer 230, 231, 232, thc primary windings of whichare in circuit with suitable sources 233, 234, 235 respectively, ofalternating current of predetermined frequcnc The frequencies of thesources are relatively different. For example, the source 235 is in thepresent instance of 70,000 cycles; 234 of 45,000 cycles and 233 of25,000 cycles. The output circuit of the detector 223 includes anindicating device 236 and a suitable battery 237 for maintaining apositive potential upon the plate with respect to the filament.

The relays 106, 107, 227 and 228 are included in circuits controlled bythe arm 133 in a manner similar to that of the relays 70, 71, 52, 48 andthe arm 80 of Figure 1, it being noted that the connections of thearcuate row of contacts of the arm 133 co1'- respond to those of the rowof contacts of the arm 80. A resistance coil 150 corresponds in functionto the resistance 81. Thus in the successive stopping positions of thearm 133 different combinations of, relays are operated, as was describedin connection with YFigure 1. The winding of the relay 229 is in serieswith the winding of both relays 227 and 228 so that the cutoff relay 229is operated whenever either of the relays 227 and 228 is operated.

In operation, the sending station of Figure 1 emits radiant energyhaving the form of high fre uency oscillations such as lven in the fourt1 column of the table of Figure 2, upon which there is impressedperiodic amplitude variations produced by modulating a supersonicfrequency by speech currents, such as given in the fifth column of thetable of Figure 2. The system of frequency changes is irregular and thusthere is imparted to the wave form of the emitted energy a disorderedSuccession of changes of frequency, so that an unauthorized stationcannot tune in suflieiently quickly to overhear the message.

At the receiving station, when the first signal is received, the arm 133being at the normal position shown, none of the relays is operated, andthus only the condenser 103 is effectively in circuit, and the closed,oscillatory circuit 101 is responsive to the emitted fundamentalfrequency, as listed in the first line of the table of Figure 2. It is lunderstood that while there may be a slight capacitative effect acrossthe left hand contact springs of the relays 106 and 107 the adjustmentof the condenser 103 may be made with such effect taken inconsideration. i

The device 110 acting as a detector produces in the primary windings ofthe transformers'll, 110 and 117 current corresponding to the su ersonicperiodic variations belng impresse upon the transmitted wave at thesending station, as listed in the table of Figure 1. In the presentinstance these variations have a frequency of from 68,000 to 69,800 forexample. Accordingly vonly the filter 220 allows the current to pass,the other filters 221 and 222 being arranged to ysuppress suchfrequencies. Since relays 227,

amaai.

of the thermionic device 223. The 'source 235 is effective, because ofthis. condition of the relays, to impress on the input of the device 223a current of the frequency of the speech-controlled current generated bythe oscillator 20 of the sending station.

The device 223 acting as a detector produces in its output circuitcurrent variations corresponding to the signal currents impressed uponthe current generated by the oscillator 20 by the signal modulator atthe sending station. The indicating device 236 is thereby caused toreproduce the signals as voice Waves. L

The high frequency currents appearing in the output circuit of the firstdetector 110 are by-passed through the condenser 119 and the rimarywinding of the transformer 118. High frequency currents are thus inducedin the secondary winding of the transformer 118 and the closed,oscillatory circuit formed thereby in combination with the condenser140. The device 120 acting as a detector produces in its output circuita rectified current the intensityr of which may be determined by asuitable choice of the normal grid potential 128 and plate. potential123, and preferably such as Will operate the sensitive relay 124 onlywhen the input circuit i`s acted upon by currents induced through thetransformer 118. Energization of the'windin ofthe relay 124 causes itsarmature to e attracted, thus closing the local circuit which includesbattery 127 and magnet 126, energizing the magnet 126 and drawingforward the awl 131 into engagement with the next fo owin tooth of theratchet Wheel 132.

hen the arm 80 moves from its first position to position 2, relays and52 are operated and the. circuit characteristics of the scndingstationare modified to emit energy of the type specified in the second line ofthe table of Figure 2. The input circ-uit of the detector 120`is now nottuned to the energy impressed thereon through the transformer 118 andthe intensity of cur.

rent in its plate circuit is reduced so that the relay 124 is released.The magnet 126 is accordingly deenergized and its armature retracted byforce of its retractile spring, so that the ratchet Wheel 132 and thearm 133 are rotated clockwise one step, to position 2. Relays 1.06, 228,and 229 are then energized, thus connecting into circuit the condenscrs104 and 141. Theinput circuits of the detectors 110, 120 are thus tunedto be responsive to the energy received at this time. The energizationof the relay connects the filter 221 into circuit and makes the source234 effective, and relay 229 .disconnects the filter 220 and source 235.The filter 221 permits the passage of currents of the vari-ationfrequencies used in position 2 (see the table of vFigure 2): and thesource 234 supplies a current of the frequency of that used at thesender. The relay' 124 is operated, and repares the pawl 131 as before.When tie arm again moves the arm 133 is moved as before, the two armscontinuing in synchronism through sueccsv message.

The invention upon which this application is based is broader than thes'ecific embodiments shown and described or the purpose of illustratingsome of the ways in which it may be employed. The scope of the inventionis therefore understood not to be limited by the., present specificdescription. I intend no limitations other than those imposed by theappended claims.

1. A radio system comprising at its sending station -a generator of highfrequency oscillations, means for producing periodic variations of saidhigh frequency oscillations arranged to be non-actuative when notaffected by signal disturbances, means for periodically changing thefrequency of said variations, a signal transmitter arranged whenoperated to cause said periodic modifying means to affect the highfrequency voscillations, whereby waves modified by signal controlledperiodic variations are produced' combined With a receiving elementarranged to intercept said Waves, a closed oscillator circuit responsiveto the high frequency oscillations, another closed oscillatory circuitresponsive to the signal controlled periodic variations and meanscontrolled by the hifrh frequency oscillations for modifying t echaracteristics of said first named oscillatory circuit.

2. A radio system comprising at its sending station a generator of highfrequency oscillations, means for producing periodic variations of saidhigh frequency oscillations arranged to be non-actuative when notaffected by signal disturbances, means for periodically changingthe'frequency of said variations, a signal transmitter arranged whenoperated to cause said periodic modifying means to affect the highfrequency oscillations, whereby Waves modified by signal controlledperiodic variations are produced; combined with a receiving element torycircuit responsive to the signal controlled periodic variations andmeans controlled by the high frequency oscillations for modifying thecharacteristics of said last named oscillatory circuit.

3. A radio system comprising at its sending station a generator of highfrequency oscillations, means for producing periodic variations of saidhigh frequency oscilla-t tions arranged to be nonactuative when notaffected by signal disturbances, means for periodically changing thefrequency of said variations, a signal transmitter arranged whenoperated to cause said periodic modifying means to affect the highfrequency oscillations, whereby waves modified by signal controlledperiodic variations are produced; combined with a receiving element;Iarranged to intercept said waves, a closed oscillator circuit responsiveto the hi h frequency oscillations, another closed osclllatory circuitresponsive to the signal controlled periodic variations and meanscontrolled by the high frequency oscillations for modifying thecharacteristics of said i closed oscillatory circuits.

4:. A radio system comprising at its sending station a generator of highfrequency oscillations, means for producing periodic variations of saidhigh frequency oscillations arranged to be nonactuative when notaffected by signal disturbances, means for periodically changing thefrequency of said variations, a signal transmitter arranged whenoperated to cause said periodic modifying means to affect the highfrequency oscillations, whereby waves modified by signal controlledperiodic variations are produced combined with a receiving elementarranged to intercept said waves, a closed oscillator circuitresponsive. to the high frequency oscillations, another closedoscillatory circuit responsive to the signal controlled periodicVariations and means controlled by the high frequency oscillations formodifying the characteristics of at least one of said closed oscillatorycircuits.

5. A radio system comprising at its sending station a generator of highfrequency oscillations, means for producing periodic variations of saidhigh frequency oscillations arranged to be nonactuative when notaffected by signal disturbances, means for periodically changing thefrequency of said variations, a signal transmitter arranged whenoperated to cause said periodic modifying means to affect the highfrequency oscillations, whereby waves modified by signal controlledperiodic variations are produced; combined with a receivingselementarranged to intercept said waves, a closed oscillator circuit rsponsfiveto the high frequency oscillations, another closed oscillatory circuitresponsive to the signal controlled periodic variations and means con-Awhen operated to cause trolled from the sending station by changes inthe waves for modifying the characteristics o f at least one of saidclosed oscillatory circuits.

u 6. A radio system comprising at its sendmg station a generator of highfrequency oscillations, means for producing periodic variations of saidhigh frequency oscillations arranged to be nonactuative when notaffected by signal disturbances, means for periodically changing thefrequency of said variations, a signal transmitter arranged periodicmodifying means to affect the high frequency oscillations, whereby wavesmodified by signall controlled periodic variations are produced;combined with a receiving element arranged to intercept said waves, aclosed oscillator circuit responsive to the high frequency oscillations,another closed oscillatory circuit responsive to the signal controlledperiodic variations and means vcontrolled from the sending station bychanges in the waves for modifying the characteristics of said lastnamed oscillatory circuit.

7. A radio system comprising at its sending station a generator of highfrequency oscillations, means for producing periodic variations of saidhigh lfrequency oscillations arranged to be nonactuative when notaffected by signal disturbances, means for periodically changing thefrequency of saidv variations, a signal transmitter arranged whenoperated to cause said periodic modifying means to affect the highfrequency oscillations, whereby waves modified by signal controlledperiodic variations are produced; combined with a receiving elementarranged to intercept said waves, a closed oscillator circuit responsiveto the high frequency oscillations, other closed oscillatory circuitresponsive to the signal controlled periodic variations and meanscontrolled from the sending stations by changes in the waves formodifying the characteristics of said closed oscillatory circuits.

8. A radio system comprising at its sending station a generator of highfrequency oscillations, means for producing periodic variations of saidhigh frequency oscillaalbv tions arranged to be non-actuative when not yraam ' ltrolled from the send-ing station by changes in the Waves formodifyimr the characteristicsof at least one of said closed oscillatorycircuits.

9. A method of transmitting radio signals which consists in modifyinghigh frequency waves by Waves of a different frequency renderedeffective by signals, changing one of said frequencies from one toanother of a plurality of diderent,` predetermined values, receiving thewaves thus produced with differently responsive instrumentalities andchanging the responsiveness of certain of said instrumentalities underthe control of the received Waves.

10. A method of transmitting radio-signais which consists of modifyinghigh frequency Waves by Waves of a diderent and continually changingfrequency rendered effective by signals, receiving the Waves thusproduced with differently responsive instrumentalities and changing theresponsiveness of said instrumentalities in step with changes infrequency of, said Waves. A

11. A method of transmitting radio signals Whichconsists in generatinghigh frequency Waves, changing the frequency of said Waves, reeiving theWaves with differently vtuned instrumentalities and changi ing thetuning of said instrumentalities under the control of the receivedwavesand in accordance with changes in the frequency of the Waves.

12A method of transmitting signals which consists of modifying highfrequency Waves by Waves of a lower and continually changing frequencyrendered eective by si nals, receiving the Waves thus produced withdifferently responsive instrumentalities and changing the responsivenessof said instrumentalities in step With changes in frequency of saidWaves.

13. A method of transmitting radio signals which consists of producingside bands above and below each of a plurality of predeterminedfrequencies by signal disturbances, suppressing the higher of each ofsaid pairs of said bands, modifying hich frequency Waves by impressingthereon t e Waves of a selected unsuppressed side band, reeiving theWaves thus produced in differently responsive instrumentalitics.supplying radiant energy of said'predeterinined -frequency and changingthe responsiveness of at least one of said instrumentalities tocorrespond to the selected unsuppressed side band. I p

14. A radio system comprising a sending station including a generator ofhigh frequency oscillations, means for producing periodic variations ofsaid high frequency oscillations arranged to be non-actuative when notaffected by vsignal disturbances, means for periodically changing thefrcquency of said high frequency oscillations in relatively lar e steps,and a signal transmitter larrange when operated to cause said periodicmodifying means to affect the high fre uency oscillations, whereby Wavesmodifie by siUnal-controlled pcriodic variations are produced and areceiving station including-,v an element arranged to intercept saidWaves, a closed, oscillatory circuit responsive tothe high frequencyoscillations, another closed, oscillatory circuit responsive to thesignz-il-controlled periodic variations and means for changing thetuning of said first-mentioned oscillatory circuit under the controlofthe received waves.

l5. A radio system comprising a sending st tion including a generator ofhigh frequenc oscillations, means for. producing pcrio ic variations ofsaid high frequency oscillations arranged to be non-actuative when notaffected by ,signal disturbances, means for periodically changing thefrequency of said high frequency oscillations in relatively large steps,and a signal 'transmitter arranged when operated to cause said periodicmodifying means to affect the high frequency oscillations wherebyWaves'inoditied by signal-controlled eriodic variations are produced anda receiving station including an element arranged to intercept saidWaves, a closed, oscillatory circuit responsive to the high frequencyoscillations, 4:mother closed, oscillatory circuit responsive to thesignal-controlled periodic variations and means controlled by thereceived Waves for changing the tuning of said first-mentioned circuitin step with changes in the frequency of said waves.

16. A radio system comprising a sending station including a generator ofhigh frequency oscillations, means for producing periodic variations ofsaid highf `frequency oscillations arranged to be non-actuative when notaffected by signal disturbances, means for. periodically changing thefrequency of said high frequency oscillations in relatively large steps,and a signal transmitter arranged when operated to cause said periodicmodifyin means to affect the high frequency oscillations, whereby wavesmodified by signal-controlled periodic variations are produced and areceiving station including an element arranged to intercept said Waves,a closed, oscillatory circuit rcsponsive to the high frequencyoscillations, another closed, oscillatory circuit responsive to thesignal controlled periodic variations and means controlled by thereceived waves for changing the tuning of said first-incutioned circuitWhenever the frequency of the high frequency oscillations is changed.

1.7. A radio system comprising a sending station including a generatorof high frequency oscillations, another generatln' of oscillations ofdiilercnt frequency, a frequency changer for periodically changing thefrequency of the first named oscillatiens in relatively lar e steps, apush-pull modulator interpos between said generators,

and a signal transmitter" cooperatively as? soeiated withthe modulator,whereby waves modified by si nal controlled periodic variations are prouced and a receiving element arranged to intercept said waves, a closed,oscillatory circuit responsive to the high frequency oscillations,another. closed, oscillatory circuit responsive to the signal-controlledperiodic variations and means for changing the tuning of saidfirst-mentioned circuit, said means including a relay, and.

19. A method of transmitting radidsig-l nals which consists in modifyinghigh frequency waves b Waves of a different frequency rendere effectiveby signals, periodically changing the frequency of said high frequencyWaves in relatively large steps, from one to another of a pluralit ofVdifferent, predetermined values, receiving thev waves thus produced withdifferently tuned instrumentalities and changing the tuning of saidinstrumentalities in step with changes in the frequency of said wavesand under the control of the received Waves.

20. A method of transmitting radio signals which consists in modifyinghigh frequency waves by waves of a lower frequency, periodicallychanging the frequency of said high frequency Waves in relatively largesteps from one to another of a plurality of different, preterrninedvalues, periodically 'changing the frequency of said second-mentionedWaves, receiving the waves thus produced with differently responsiveinstrumentalities and selecting under the control of the received wavesinstrumentalities tuned respectively to the values of the higher andlower frequencies at any particular time.

21. A method of transmitting radio signals which consists in modifyinghigh frequency waves by waves of a lower frequency rendered effective bysignals, periodically changing the frequency of said high frequencywaves, periodically changing the frequency of said second-mentionedwaves, receiving the waves thus produced with differently responsiveinstrumentalities and set another closed osc igsaaaai lecting'funder thecontrol of the receivedl i waves and in step with changes in thefrequency'characteristic-v of said waves, instrumentalitiestunedgrespectively to the values of said', higher an'dlower frequencies.

22.v Ay radio system comprising at its sending 'station a generator ofhigh frequency oscillations,-v means for producing periodic variationsof said high frequency oscillations arranged to benen-actuative whennotaffected by si al disturbances, means for periodically c anging thefrequency of said variations, means for periodically changin thefrequency' of said high frequency osci lations in relatively largesteps, a signal transmitter arranged when operated to cause saidperiodic modifying meansto affect the -highffrequency oscillat1ons,whereby waves modified by signal controlled periodic variations areproduced; combined with a receiving element arranged to intercept saidwaves, a closed oscillator circuit responsive to the' vhigh frequencyoscillations, another clocd'fcscillatory circuit responsive to thesignal ,controlled periodic variations and means ,controlled by the highfrequenc oscillati'ns for modifying the characteristics of at least oneof said closed oscillatory circuits; p

23.-`A radio system comprising at its sending station a generator ofhigh' frequency' oscillations, another generator of `oscillations ofdifferent frequency, a frequency changer for periodically changing thefrequency of the last named oscillations, a frequency changer forperiodically changing the frequency of the first named oscillations inrelatively large steps, a push-pull modulator interposed between saidgenerators, a signal transmitter co-operatively associated with themodulator, whereby waves modified by signal controlled periodicvariations are produced; combined with a receiving element arranged tointercept said waves, a closed oscillatory circuit responsive to thehigh frequency oscillations, latory circuit responsive to the signalcontrolled periodic variations and means controlled by the hi hfrequency oscillations for modifying the cliaracteristics of at leastone of said closed oscillatory circuits.

24. A method of transmitting radio lsignals which consists in modifyinghigh frequency Waves by waves of a different and continually changingfrequency rendered effective by signals, eriodically changing thefrequency of said igh frequency waves, receiving the Waves thus producedwith differently responsive instrumentalities and changing theresponsiveness of said instrumcntalities under the control' of thereceived waves. l

25. A method of transmitting radio signals which consists in modifyinghigh frcquency waves by waves of a different fre- A quency, periodicallychanging the frequency of said second-mentioned waves, receiving thewaves thus produced with differently responsive instrumentalities andselecting under the control of the received waves instrumentalitiestuned to said second-mentioned frequency in step with changes in suchfrequency. v y 26. A method of transmitting radio signals which consistsin modifying high frequency waves by waves of a lower frequency renderedeffective by signals and continually 'changing in frequency within arange determined by' the signals, periodically changing the meanfrequency of the frequency range of said second-mentioned waves,receiving the Waves thus produced with differently responsiveinstrumentalities and selecting under the control of the received Wavesmstrumentalities tuned to said frequency range in step with changes inthe mean frequency of the frequency range.

27. A radio system comprisin at its sending station a generator of higfrequency oscillations, means for periodically changing the frequency ofsaid high frequency oscillations in relatively large steps, means fortransforming signalcurrents into a supersonic frequency range andretaining the characteristics of the signal currents, means for changingperiodically and continuously the supersonic frequency range employed,means for modulating the currents generated by the high frequencygenerator according to the transformed supersonic signal currents,whereby Waves modified by signal con-- trolled periodic variations areproduced; combined With a receiving element arranged to intercept saidWaves, a closed oscillatory circuit responsive to each series of highfrequency oscillations employed, other closed 4oscillatory circuitsresponsive to the signal controlled periodic 'variations employed andmeans controlled by the high frequency oscillations for modifying thecharacteristics of said first named oscillatory circuit.

28. A radio system comprisinor at its sending station a generator ofhignh frequency oscillations, means for periodically changing thefrequency of saidhigh frequency oscillations in relatively large steps,means for transforming signal currents into a supersonic frequency rangeand retaining the characteristics of the signal currents, means forchanging periodically and continuously the supersonic frequency rangeemployed, means for modulating the currents generated by the highfrequency generator according to the transformed supersonic signalcurrents, whereb Waves modified by -signal controlled perio icvariations are produced; combined with a receiving element arranged tointercept said Waves, `a closed oscillatory circuit responsive to eachseries of high frequency oscillations employed, other closed oscillatorycircuits responsive to the signal controlled periodicv variationsemployed, and means controlled by the high frequency oscillations formodifying the characteristic/s of said last named oscillator circuits.

29. A radio system comprising at its send- Y ed by the high frequencygenerator accordt ing to the transformed supersonic signal currents,whereby Waves modified by signal controlled periodic variations areproduced; combined With a receiving element arranged to intercept saidWaves, a closed oscillatory circuit responsive to each series of highfrequency oscillations employed, other closed oscillatory circuitsresponsive to the signal controlled periodic variations employed, andmeans controlled by the high frequency oscillations for modifying thecharacteristics of said closed oscillatory circuits.

30. A radio system comprising at its sending station a generator of highfrequency oscillations, means for periodically changing thev frequencyof said high frequency oscillations in relatively large steps, means fortransforming signal currents into 'a supersonic frequency range andretaining the characteristics of the signal currents, means for changingperiodically and continuously the supersonic frequency range employed,means for modulating the currents generated by the high frequencygenerator according to the transformed supersonic signal currents,Whereb waves modified by signal controlled perio io variations areproduced; combined with a receiving element arranged to intercept saidwaves, a closed oscillatory circuit responsive to each series of highfrequency oscillations employed, other closed oscillatory, circuitsresponsive to the signal controlled periodic variations and meanscontrolled by the high frequency oscillations for modifying thecharacteristics of at least one of said closed oscillatory circuits.

31. A radio system comprising at its sending station. a generator ofhigh frequency oscillations, means for periodically changing thefrequency of said high frequency oscillations in relatively large steps,means for transforming signal currents into a supersonic frequency rangeand retaining the characteristics of the signal currents, means forchanging periodically and continuously the supersonic frequency rangeemploye means for modulating the currents generated by the highfrequency generator according to the transformed supersonic signalcurrents, whereby Waves modified by signal controlled periodicyariationsare produced; combined with a receiving element arranged to interceptsaid Waves, a closed oscillatory circuit responsive to each series oflhigh frequency oscillations employed, other closed oscillatory circuitsresponsive to the signal controlled periodic variations employed, andmeans controlled from the sending station by changes in the Waves formodifying the characteristics of said first named oscillatory circuit.

32. A radio system comprising at its sending station a generator of highfrequency oscillations, means for periodically changing the frequency ofsaid high frequency oscillations in relatively large steps, means fortransforming signal currents into a supersonic frequency range andretaining the characteristics of the signal currents, means for changingperiodically and continuously the supersonic frequency range employed,means for modulating the currents generated by the high frequencygenerator according to the transformed supersonic signal currents,whereby Waves are produced; combined with a receiving element arrangedto intercept said Waves, a closed oscillatory circuit responsive to eachseries of high quency oscillations employed, other closed oscillatorycircuits responsive to the signal controlled periodic variationsemployed, and means controlled from the sending station by changes inthe waves for modifying the characteristics of said last namedoscillatory circuit.

33. A radio system comprising at its sending station a generator of highfrequency oscillations, means for periodically changing the frequency ofsaid high frequency oscillations in relatively large steps, means fortransforming signal currents into a supersonic frequency range andretaining the characteristics of the signal currents, means for changingperiodically and continuously the supersonic frequency range employed,means for modulating the currents generated by the high frequencygenerator' ac cording to the transformed supersonic signal currents,signal controlled periodic -variations are produced; combined with areceiving element arranged to intercept said Waves, a closed oscillatorycircuit responsive to each series of high frequency oscillationsemployed, other closed oscillatory circuits responsive to the signalcontrolled periodic variations em loyed, and means controlled from thesending station by changes in the Waves for modifying thecharacteristics of said closed oscillatory circuits.

34. A radio system comprising at its send- Whereby Waves modified by ingstation a generator of high frequency oscillations, means forperiodically changing the frequency of said high frequency oscillationsin relatively large steps, means for transforming signal currents Iintoa supersonic frequency range and retaining the characteristics of thesignal currents, means for changing periodically and continuously thesupersonic frequency range employed, means for modulating the currentsgener'- ated by the lhigh frequency generator according to thetransformed supersonic signal currents, whereby Waves modified by signalcontrolled periodic variations are produced; combined with a receivingelement arranged to intercept said waves, a closed. oscillatory circuitresponsive to each series of high frequency oscillations employed, otherclosedoscillatory circuits responsive to the signal controlled periodicvariations employed, and means controlled from the sendingr station bychanges in the Waves for modifying theI characteristics of at least oneof said closed oscillatory circuits.

35. A radio system comprising at its sending station a generator' ofhigh frequency oscillations, means for periodically changing thefrequency of said high frequency oscillations in relatively large steps,'means for transforming signal currents into a supersonic frequencyrange and retaining the characteristics ofthe signal currents, means forchanging periodically and continuousl the supersonic frequency rangeemployeti means for modulating the currents generated by the highfrequency generator according to the transformed supersonic signalcurrents, whereby waves modified by signal controlled periodicvariations are produced; combined with a receiving element arranged tointercept said waves, a closed oscillatory circuit responsive to eachseries of high frequency oscillations employed, other closed oscillatorycircuits responsive to the signal controlled periodic variationsemployed, and means controlled by the high frequency os cillations formodifying the characteristics of at leastl one of said closedoscillatory circuits.

36. A radio system comprising at Iits send ing station a generator ofhighfrequency oscillations, means for periodicall changing the frequencyof said high requency oscillations in relatively large steps, meansfortransforming signal currents into a supersonic frequency range andretaining the characteristics of the signal currents, means for changingperiodically and continuously the supersonic frequency range employed,means for modulating the currents generated by the high frequencygenerator according to the transformed supersonic signal currents,whereby Waves modified by signal controlled periodic variations areproduced; combined with a receiving element arranged to intercept saidwaves, a closed oscillatory circuit responsive to each series of highfrequency oscillations employed, other closed oscillatory circuitsresponsive to the si nal controlled periodic variations employe andmeans controlled from the sending station by changes in the waves formodifying the characteristics of atleast one of v said closedoscillatory circuits.

37. A radio system comprisin at its sendthe supersonic frequency rangeemployed,.

means for modulating the currents generated by the high frequencygenerator according to the transformed vsupersonic voice currents,

' whereby-waves modified by voice controlled periodic variations areproduced; combined with a receiving element arranged to intercept saidWaves, a.closed oscillatory circuit; responsive to each series of highfrequency oscillations employed, other closed oscillatory circuitsresponsive to the voice controlled periodic variations employed, andmeans controlled by the high frequency oscillations for modifying thecharacteristics of at least one of said closed oscillatory circuits. t

38. A radio system .comprisin at its sending station a generator of higfrequency oscillations, means for periodically changing the frequency ofsaid high frequency oscillations in relatively large steps, means fortransforming voice currents into a supersonic frequency range andretaining vthe characteristics of the si nal currents, means forchanging periodicay and continuousl the supersonic frequency rangeemploye means for modulating the currents generated by the highfrequency generatoraccording to the transformed su ersonic voicecurrents, whereby waves modi ed by voice controlled periodic variationsare produced; combined with a receiving element arranged to interceptsaid waves, a closed oscillatory4 circuit selectively connecting saidmodulation ciroscillations employed, other closed oscillatory circuits'responsive to the voice controlled periodic variations employed, andmeans controlled from the sending station by changes inthe waves formodifying the characteristics of at least one of said closedoscillatoryvcircuits. Y

39. A radio system comprising a sending station including a generator'ofhigh freuency oscillations, means for modulating t'ehigh1frequencyoscillations and means for changing thefrequency range of saidmodulations, and a receiving station includ'-v ing means for producingcurrent corresponding in frequency with said modulations, anindicator,circuits interposed between said current producing means and theindicatorv and tuned respectively to the different frequency ranges. .ofsaid modulations and meansy controlled by the received energy for vinstation including a tuned receiving circuit, a detector for producingcurrent corre? sponding in frequency to the frequency of saidmodulations, an indicator, circuits interposed between the detector andthe indicator and tuned respectively to the different frequency rangesyof said modulations, and means controlled by the received energy for,changing the tuning of said receiving circuit in accordance with thedifferent frequencies of the high frequency oscillationsand for cuits tothe indicator in `accordance with changes in the frequency ranges of themodulations impressed upon the high frequency oscillations.

In testimony whereof I hereunto afiix my signature.

JOHN HAYs HAMMOND, Jar

selectively connecting said last-mentionedV

